1. FIELD OF THE INVENTION
The invention is related to high voltage resistance cables and more specifically to ignition cables for spark ignited internal combustion engines.
2. DESCRIPTION OF THE PRIOR ART
The use of ignition or spark plug cables having a resistance greater than 100 ohms/foot for reducing radio frequency ignition noise in automotive vehicles is well known. These ignition cables have nonmetallic conductor elements enclosed in an insulator jacket. The nonmetallic conductor elements may consist of individual threadlike filaments impregnated with a conductive material, such as graphite. Alternately, a group of impregnated filaments may be gathered together in a bundle or roving and the roving impregnated with a conductive rubber as taught by Barker et al in U.S. Pat. No. 3,284,751. A non-conductive fiber is braided over the conductive rubber and overlaid with an insulating layer and protective jacket. Alternately, the ignition cable may consist of a plurality of conductive fibers encased by a semi-conductive polytetrafluorethylene overcoat as disclosed by King in U.S. Pat. No. 3,991,397. In another alternative, the nonmetallic conductor core element may consist of a non-conductive fiber bundle tension member circumscribed by a layer of conductive paint as taught by Miyamoto et al in U.S. Pat. No. 4,363,019. In U.S. Pat. No. 4,375,632, Miyamoto et al further teach the use of two resistive layers separated by a conductive stripping layer, the inner resistive layer being a conductive carbon paint and the outer resistive layer being a semi-conductive ethylenepropylene rubber. In U.S. Pat. 3,683,309, Hirose teaches an ignition cable having a nonmetallic fiber bundle having a film of conductive nonmetallic particles, such as graphite or carbon dispersed in a binding agent. The nonmetallic fiber bundle is covered with two layers of a magnetic and conductive synthetic resin coating. Vitale, in U.S. Pat. 3,680,027, and Kanamori et al, in U.S. Pat. No. 4,748,436, disclose an ignition cable having a fiberglass bundle tension member, a conductive silicon rubber overlay, an insulating rubber layer, a glass fiber overbraid and an insulating jacket. Carini et al, in U.S. Pat. No. 3,876,462, disclose an insulated cable having a central metal conductor, an insulating layer and a semi-conductive cross-linked polyolefin external layer.
The invention is an improved ignition cable of the type taught by the referenced prior art having improved heat stability and electrical integrity.